Interference fit control for the assembly of rotary parts

Abstract

A rotary assembly for an aircraft engine is disclosed. A shaft is mounted for rotation about a central axis and a rotary part is mounted on the shaft for common rotation therewith. The rotary part has an axial end portion extending away from a center of mass of the rotary part, the axial end portion having a radial thickness smaller than that of the rotary part at an axial location aligned with the center of mass. The shaft and the rotary part have an interface defining an interference fit between the shaft and the axial end portion of the rotary part. The interface is located at a distance along the central axis from the center of mass. An undercut is defined in the rotary part. The undercut extends axially from adjacent the interface towards the center of mass.

The invention claimed is: 
     
       1. A rotary assembly for an aircraft engine, the rotary assembly comprising:
 a shaft mounted for rotation about a central axis; 
 a rotary part mounted on the shaft for common rotation with the shaft, the rotary part having an axial end portion extending away from a center of mass of the rotary part, the axial end portion having a radial thickness smaller than that of the rotary part at an axial location aligned with the center of mass, the shaft and the rotary part having an interface defining an interference fit between the shaft and the axial end portion of the rotary part, the interface located at a distance along the central axis from the center of mass; and 
 an undercut defined in the rotary part, the undercut extending axially from adjacent the interface towards the center of mass, the undercut having an axial length taken along the central axis, the axial length being between about 10% and about 50% of the distance of the interface from the center of mass. 
 
     
     
       2. The rotary assembly as defined in  claim 1 , wherein the rotary part includes a rotor hub, wherein the axial end portion defines an arm portion of the rotor hub extending along the shaft, the arm portion and the shaft defining the interface. 
     
     
       3. The rotary assembly as defined in  claim 1 , further comprising a radial clearance between the rotary part and the shaft, the radial clearance extending axially from the interface, wherein the undercut defines a zone of radial increase of the radial clearance. 
     
     
       4. The rotary assembly as defined in  claim 1 , wherein the radial thickness of the axial end portion is taken at a location aligned with the interface, wherein the undercut has a maximal radial depth between about 10% and about 50% of the radial thickness. 
     
     
       5. The rotary assembly as defined in  claim 1 , wherein the undercut extends axially from the interface. 
     
     
       6. The rotary assembly as defined in  claim 1 , wherein the undercut is a groove defined in a shaft-facing surface of the rotary part, the groove extending circumferentially about the shaft. 
     
     
       7. The rotary assembly as defined in  claim 1 , wherein the axial location is an axial center of the rotary part. 
     
     
       8. The rotary assembly as defined in  claim 1 , wherein the interface is a first interface, the rotary part and the shaft having a second interface defining an interference fit between the shaft and the rotary part, the second interface located along the central axis on an opposite side of the center of mass with respect to the first interface. 
     
     
       9. A rotary assembly of an aircraft engine, comprising:
 a shaft mounted for rotation about a central axis; 
 a rotor mounted on the shaft for common rotation, the rotor including a rotor hub coupled to the shaft, the rotor hub having an axial center and an arm portion extending away from the axial center; 
 an interface defining an interference fit between the shaft and the arm portion, the interface located at a distance along the central axis from the axial center; 
 an undercut defined in the rotor hub, the undercut extending from the interface towards the axial center, the undercut has an axial length taken along the central axis, the axial length being between about 10% and about 50% of the distance of the interface from the axial center; and 
 a radial clearance between the rotor hub and the shaft, the radial clearance extending from the interface, wherein the undercut defines a zone of radial increase of the radial clearance. 
 
     
     
       10. The rotary assembly as defined in  claim 9 , wherein the undercut has a radial depth between about 10% and about 50% of a radial thickness of the arm portion taken at location aligned with the interface. 
     
     
       11. The rotary assembly as defined in  claim 9 , wherein the undercut is a groove extending circumferentially about the shaft. 
     
     
       12. The rotary assembly as defined in  claim 9 , wherein the interface is a first interface, the rotor hub and the shaft having a second interface, the second interface defining an interference fit between the shaft and the rotor hub separate from the interference fit of the first interface, the second interface located along the central axis on an opposite side of the axial center with respect to the first interface. 
     
     
       13. The rotary assembly as defined in  claim 12 , wherein the arm portion is a front arm portion of the rotor hub, the rotor hub including a rear arm portion extending away from the axial center in a direction opposite to the front arm portion along the shaft, the rear arm portion and the shaft defining the second interface. 
     
     
       14. The rotary assembly as defined in  claim 12 , wherein the first interface and the second interface are located at respective axial ends of the rotor hub. 
     
     
       15. The rotary assembly as defined in  claim 14 , wherein the radial clearance extends continuously to the second interface. 
     
     
       16. The rotary assembly as defined in  claim 9 , wherein the rotor has a center of mass, wherein the rotor hub has a non-uniform mass distribution along the central axis, the axial center of the rotor hub aligned with the center of mass of the rotor. 
     
     
       17. A rotary assembly for an aircraft engine, the rotary assembly comprising:
 a shaft mounted for rotation about a central axis; 
 a rotary part mounted on the shaft for common rotation with the shaft, the rotary part having an axial end portion extending away from a center of mass of the rotary part, the axial end portion having a radial thickness smaller than that of the rotary part at an axial location aligned with the center of mass, the shaft and the rotary part having an interface defining an interference fit between the shaft and the axial end portion of the rotary part, the interface located at a distance along the central axis from the center of mass; and 
 an undercut defined in the rotary part, the undercut extending axially from adjacent the interface towards the center of mass, wherein the radial thickness of the axial end portion is taken at a location aligned with the interface, and the undercut has a maximal radial depth between about 10% and about 50% of the radial thickness. 
 
     
     
       18. The rotary assembly as defined in  claim 17 , wherein the axial location is an axial center of the rotary part. 
     
     
       19. The rotary assembly as defined in  claim 17 , wherein the interface is a first interface, the rotary part and the shaft having a second interface defining an interference fit between the shaft and the rotary part, the second interface located along the central axis on an opposite side of the center of mass with respect to the first interface. 
     
     
       20. The rotary assembly as defined in  claim 19 , further comprising a radial clearance between the rotary part and the shaft, the radial clearance extending axially from the interface, wherein the undercut defines a zone of radial increase of the radial clearance, wherein the radial clearance extends continuously to the second interface.